Generally, lift trucks are well known as an automotive working machine which is resorted to freight shipping (cargo handling) jobs from ground to higher position. The lift trucks of this sort are largely constituted by an automotive vehicle body provided of front and rear wheels, a boom liftably provided on the vehicle body for derricking motions, a working tool like a cargo handling tool rotatably supported at a fore end of the boom, and a tool operating cylinder located between the cargo handling tool and the boom for turning the cargo handling tool in upward and downward directions relative to the boom (e.g., as known from Japanese Patent 2,559,831 and International Publication WO 89/00972).
In the case of a lift truck of this sort, the boom is lowered into a flatly folded position on the side of the ground at the time of loading freight goods onto a fork of the cargo handling tool, and then turned upward to lift and transfer the freight goods to a higher level from the ground. At this time, the tool operating cylinder which is provided between the boom and the working tool functions to turn the cargo handling tool according to the elevation angle of the boom to maintain the fork of the cargo handling tool constantly in a horizontal posture for transferring the freight goods in a stabilized state.
By the way, the tool operating cylinder which is used on the above-described lift truck is normally constituted by a tube which is attached to the boom on the side of its bottom end, a piston which is slidably fitted in the tube, and a rod which is attached to the piston at its base end and connected to a cargo handling tool at its fore end which is projected out of the tube. When the boom is lowered into a flatly folded position on the side of the ground, the fore end of the tool operating cylinder is projected downward toward the ground surface from the lower side of the vehicle body.
Therefore, when the vehicle is on a rocky ground and driven in reverse direction with the boom in the flatly folded position, it is very likely for the rod of the working cylinder which is projected downward from the lower side of the vehicle body to be directly collided against a rock or similar obstacle on the ground surface even if the lower side of the vehicle has passed clear of the rock. The collision against such a rock can result in fracture of the working cylinder.
On the other hand, as to other automotive working machines by the prior art, there has been known a hydraulic excavator which is provided with an excavating bucket along with a bucket operating hydraulic cylinder, and in which a tubular or pipe-like cover is employed as a protector and arranged to enshroud a rod portion which is projected out of a tube of the hydraulic cylinder (e.g., as known from Japanese Patent Laid-Open No. 2001-82414).
The protector cover in the just-mentioned prior art is a tubular shape and larger in diameter than the hydraulic cylinder tube. One longitudinal end of the cover tube is attached to the fore end of the rod which is projected out of the hydraulic cylinder tube. Accordingly, the outer peripheral side of the hydraulic cylinder rod is constantly enclosed in the cover tube to prevent collisions of sand and soil against the hydraulic cylinder rod.
However, in the case of the prior art cover tube for a hydraulic cylinder, as mentioned above, one longitudinal end of the cover tube is attached to the fore end of the hydraulic cylinder rod. Therefore, when sand and soil comes into colliding contact with the cover tube, the impacts of collision are transmitted to the hydraulic cylinder rod to cause deformations and damages to the rod.
Further, in the case of the cover tube just mentioned, the cover is formed in a tubular shape to enclose the hydraulic cylinder tube and rod from the outer peripheral side thereof. Therefore, sand and soil tend to deposit between the cover and the hydraulic cylinder rod to hamper smooth operations of the hydraulic cylinder.